Vaporizing oil burner



Dec. 20, 1966 e. R. SMITH 3,292,682

VAPORIZING OIL BURNER Filed April 13, 1964 2 Sheets-Sheet 1 /0 INVENTOR. ozaoxv A 504/ TH BY WWW W ,4770 NIP/5 Dec. 20, 1966 G. R. SMITH 3,292,682

VAPORIZ ING OIL BURNER i5 477 AIYEYS United States Patent 3,292,682 VAPORIZING OIL BURNER Gordon R. Smith, Stillwater, Minn., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Apr. 13, 1964, Ser. No. 359,126 4 Claims. (Cl. 158-45) This invention relates to a method for volatilization of fluid fuels and to burners employing the method.

In oil burners of the type used for domestic heating it is conventional either to spray the oil (a No. 1 or No. 2 fuel oil) under pressure into the fire box together with a suitable supply of air; or without pressure to employ a puddle of oil or to permit the oil to seep or trickle into a firepot. The former has the disadvantage that the spray is through a fine orifice which readily becomes plugged by fine particles or may become enlarged by wear or the diameter of which may also be changed by corrosion. The latter two methods have the common disadvantage that for an appreciable time before combustion the oil may be at temperatures in the cracking range without actually burning and this tends to produce soot and smoke, or may lead to foul odors or caking. In all cases it is desired to obtain a combustible mixture of air and fuel vapors.

It is an object of this invention to provide a method for forming combustible mixtures of vaporized fuel and air with substantial avoidance of cracking of the fuel.

A further object of this invention is to provide an oil burner in which the tendency to smoke is minimized.

Yet other objects of the invention will become evident from the disclosure herein.

In accordance with the above and other objects of the invention it has been found that by employing a crossflow heat-exchanger in the flue line of an oil burner and preheating the intake air by the said heat-exchanger, and desirably further preheating the air by passage around the fire box and combustion chamber of the oil burner, the temperature of the air can be brought to a sufficiently high temperature that oil admitted into the air stream (as will become evident hereinafter) is substantially instantaneously volatilized and thoroughly mixed therewith to give a combustible mixture with substantially no crack ing of the oil.

The success of this method depends upon the employment of a relatively simple device which permits of rapid distribution of the liquid oil over a very large area in intimate contact with substantially the entire air stream. This avoids the difficulties attendant upon having droplets of oil which as is well-known have a minimum surface and also the difiiculties when greater masses, e.g. puddles, of oil are exposed to a stream of hot air.

The device in a preferred embodiment is basically a prism of triangular undulate ceramic sheets adhered at the points of intersection of ridges. One face of the prism which is the side from which the hot air stream enters, is smaller than either of the other faces. The latter faces are not necessarily equal in areas but should be within a ratio of not more than about 2 to 1. The faces through which the stream of gas passes should have a ratio approximately equal within about 50 percent to the ratio of the volume of hot combustible mixture produced to the volume of hot air. Suitable ceramic materials are available by the same procedures as described in my US. Patent No. 3,088,271.

The prism is disposed horizontally that is with the undulate sheets being generally vertical and the undulations non-horizontal and preferable at inclinations of about 4-5 Oil is applied along an upper edge by means such as a slotted distributor which efiects substantially uniform distribution along the entire edge.

The face of the prism which is not employed for air passage may be blocked .ofr by application of ceramic or conveniently by an electrically heated primer which serves to initiate volatilization of the oil.

Similar structures are made of materials such as metal and even organic materials for particular purposes, for example, in humidifiers, chemical reactors and other such operations. It is generally not necessary that these prismatic vaporizers of the invention be absorbent because volatilization proceeds rapidly and substantially no wicking action can occur. It is preferred that these structures be no more porous than well-fired ceramics for use in the oil burner of the invention where the refractoriness of ceramics is particularly useful.

The uneven surfaces of ceramics are further advantageous as providing somewhat greater surface area for volatilization.

The operation of my invention will become evident from a consideration of the drawings herewith wherein:

FIGURE 1 is a top view of an oil burner of the invention.

FIGURE 2 is a side elevation broken away to show partial cross-sections along the line 2-2 of FIGURE 1.

FIGURE 3 is an end elevation broken away to show partial cross-sections along the line 33 of FIGURE 2.

FIGURE 4 is a cross-sectional view along the line 44 of FIGURE 2.

FIGURE 5 is a cross-sectional detail along line 55 of FIGURE 4.

Referring now to the figures, in which identical parts bear the same indicia, air is drawn into the outer casing 10, having supports 12, at port 14 through flanged closure 16 and passes around fire box or combustion chamber 20 and plenum -40 connected by duct 33 and attached to the under side of closure 11 of the outer casing 10, to fan 18 rotated by motor M or other suitable means within fan casing 19 attached to the outer casing 10 over port 15 in the outer casing. In passing between the outer casing and fire box 20 and plenum 40 the air serves as insulation so that the outer casing is not much more than warm to the touch when the burner is operating. Also, the air is warmed slightly by heat which would otherwise be lost. The air as it enters the fan is thus slightly preheated and is blown upward through butterfly damper 50 (shown in partially open position as at the start up of the burner in FIGURES 1 and 3) into the cool end plenum 62 of the housing 60 (attached to the upper surface of closure 11) and through cross-flow heat-exchanger within housing 60 where it is heated by the flue gases (after the burner is operating) to a temperature above about 500 C. and passes into the hot end plenum of housing 60, the plenum serving as means connecting the cross-flow heat-exchanger and fire box, and then passes, with increase in linear flow rate, through fuel oil evaporator where it evaporates sufiicient fuel to form a combustible mixture which burns in fire box 20. The very hot line gases from fire box 20 pass through ceramic combustion grid 22 (which is very hot and assures complete combustion as well as acting as a flame arrestor) in duct 30 into plenum 40 and from there upward through cross-flow heat-exchanger 70 (where incoming air is heat-ed as noted above) and into a suitable air heater or other device for recovery of sensible heat and disposal of flue gases, here represented by collar 98 to which such a device may be attached as indicated in FIGURE 2 by the duct 99.

Returning to the details of construction, in FIGURE 2, it will be seen that fire box or combustion chamber 20 and plenum 40 have insulating ceramic linings and duct 30 is shown welded therebetween. It will be understood that the method of construction is a matter of convenience and is not critical to the invention. Thus it is particularly convient to Weld fire box 20, plenum and housing to closure 11 which is then bolted to flange 13 of outer casing 10. Housing 60 is provided with a first opening 64, having flange 65, within which heat exchanger rests on the surface of closure 11 and i positioned by suitable clips and refractory packing, and with a second opening 66 having flange 67 within which the oil evaporator subassembly 82, shown in cross-section in FIGURE 5, is positioned. Housing 60 is further fitted with thermostatic control means 52 in hot end plenum adapted to control the opening of butterfly valve 50 by movement of arm 54 and shaft 56 adjustable as to length by positioning of yoke 58 attached to lever arm 55 having open and closed stopping means 57 and 59 respectively.

Oil evaporator subassembly 82 has base plate 83 which serves as closure of opening 66 and support for frame 84 having wing ledges 85 effecting closure of opening 17 through closure 11 into fire box 20. Frame 84 has internal retaining means 86 for positioning oil evaporator 90 therein and attachment means, such as flanges 87, for attachment of heater block 93, which serves to retain oil evaporator or volatilizer 90 and oil distributor 91, and for the further attachment of drip surface 88.

Oil distributor 91 is provided with inlet 92 and distribution slot 94 and is conveniently constructed by folding a sheet of metal back on itself at the approximate point of attachment of the inlet, cutting one leg slightly below the bend and welding the cut off piece to the other leg so as to leave an aperture or small slot along the line of cutting.

Heater block 93 is provided with insulated leads 95 connected to a suitable source of electricity (not shown) and, in addition to incidentally retaining oil evaporator 90 as noted, is employed to provide heat to the fuel at start-up of the burner.

Ignition means are provided for the burner as shown in the figures by a solitary electrode 96 having well insulated lead 97 and spark plug 25 and are energized by the high voltage leads of a suitable, conventional, high voltage transformer (not shown), the entire body of the burner being attached to the mid-tap or ground lead of the transformer at any convenient point. Electrode 96 thus arcs to frame 84 or drip surface 88 (which is grounded to frame 84) at a point near oil distributor 90 and spark plug 25 arcs in the vapor stream in fire box 20 thus doubly insuring ready ignition.

Those skilled in the art will readily appreciate that modifications in the design of burner incorporating fuel volatilizers are possible without the scope of the present invention which is only limited by the appended claims.

What is claimed is:

1. In a burner adapted for the combustion under forced draft of combustible mixtures of vaporized fluid fuel and air and provided with ignition means and a fire box, the combination of (I) a cross-flow heat-exchanger adapted to pass at least a part of flue gases from said fire box in one direction and to pass intake air under forced draft in another direction at substantially right angles,

(II) connection means connecting said cross-flow heatexchanger at the face of egress of intake air to said fire box,

(III) at least one prismatic fuel volatilizer consisting essentially of an assemblage of superimposed corrugated ceramic sheets of triangular shape having the axes of corrugation in adjacent sheets nonparallel and mutually at angles of from about 90 to about said sheets being ceramically adhered at points of contact of ridges of consecutive sheets, said fuel volatilizer having one face of'lesser area than either other face and being positioned in said connection means with said axes of corrugation in perpendicular planes in directions other than horizontal and with said face of lesser area adapted to receive air after passage through said heat-exchanger and one other face adapted to discharge air into 5 said connection means nearer said fire box and (IV) means distributing fluid fuel substantially uniformly along an upper edge of said prismatic fuel volatilizer. 2. In a burner adapted for the combustionunder 1O forced draft of combustible mixtures of vaporized fluid fuel and air and provided with ignition means and a fire box, the combination of (I) a cross-flow heat-exchanger adapted to pass at least a part of flue gases from said fire box in one direction and to pass intake air under forced draft in another direction at substantially right angles,

(II) air intake ducting means providing intake air to said cross-flow heat-exchanger, at least a part of said ducting means being external to and at least in part surrounding said fire box,

(III) connection means connecting said cross-flow heat-exchanger at the face of agress of intake air to said fire box,

(IV) at least one prismatic fuel volatilizer consisting rugated ceramic sheets of triangular shape having the axes of corrugation in adjacent sheets nonparallel and mutually at angles of from about 90 to about 120, said sheets being ceramically adhered.

30 at points of contact of ridges of consecutive sheets, said fuel volatilizer having one face of lesser area than either other face and being poitioned in said connection means with said axes of corrugation in perpendicular planes in directions other than hori-,

cent sheets being adhered at points of contact of ridges,

the edges of said sheets defining faces of a prism.

4. A process for the volatilization of a vaporizable 5O liquid material compirsing the steps of (I) continuously supplying said liquid material to an upper edge of an assemblage of generally vertically disposed superimposed corrugated triangular sheets, the edges of said assemblage being defined by the apices of said sheets; the axes of corrugation of all sheets being at an angle from horizontal and of adjacent sheets being non-parallel and mutually at angles of from about 90 to about 120 and adjacent sheets being adhered at points of contact of 60 ridges and (II) passing carrier gas, at a temperature suflicient to provide heat of vaporization for said liquid mate-.

rial, through said assemblage.

References Cited by the Examiner UNITED STATES PATENTS 1,450,338 4/1923 Sklovsky 15s 4.5 2,735,481 2/1956 Reichhelm 158-36 3,088,271 5/1963 Smith 60-30 FOREIGN PATENTS 1,058,077 5/1959 Germany.

FREDERICK L. MATTESON, JR., Primary Examiner. 75 R. A. DUA, Assistant Examiner.

essentially of an assemblage of superimposed corzontal and with said face of lesser area adapted to, 

1. IN A BURNER ADAPTED FOR THE COMBUSTION UNDER FORCED DRAFT OF COMBUSTIBLE MIXTURES OF VAPORIZED FLUID FUEL AND AIR AND PROVIDED WITH IGNITION MEANS AND A FIRE BOX, THE COMBINATION OF (I) A CROSS-FLOW HEAT-EXCHANGER ADAPTED TO PASS AT LEAST A PART OF FLUE GASES FROM SAID FIRE BOX IN ONE DIRECTION AND TO PASS INTAKE AIR UNDER FORCED DRAFT IN ANOTHER DIRECTION AT SUBSTANTIALLY RIGHT ANGLES, (II) CONNECTION MEANS CONNECTING SAID CROSS-FLOW HEATEXCHANGER AT THE FACE OF EGRESS OF INTAKE AIR TO SAID FIRE BOX, (III) AT LEAST ONE PRISMATIC FUEL VOLATILIZER CONSISTING ESSENTIALLY OF AN ASSEMBLAGE OF SUPERIMPOSED CORRUGATED CERAMIC SHEETS OF TRIANGULAR SHAPE HAVING THE AXES OF CORRUGATION IN ADJACENT SHEETS NONPARALLEL AND MUTUALLY AT ANGLES OF FROM ABOUT 90* TO ABOUT 120*, SAID SHEETS BEING CERAMICALLY ADHERED AT POINTS OF CONTACT OF RIDGES OF CONSECUTIVE SHEETS, SAID FUEL VOLATILIZER HAVING ONE FACE OF LESSER AREA THAN EITHER OTHER FACE AND BEING POSITIONED IN SAID CONNECTION MEANS WITH SAID AXES OF CORRUGATION IN PERIPENDICULAR PLANES IN DIRECTIONS OTHER THAN HORIZONTAL AND WITH SAID FACE OF LESSER AREA ADAPTED TO RECEIVE AIR AFTER PASSAGE THROUGH SAID HEAT-EXCHANGER AND ONE OTHER FACE ADAPTED TO DISCHARGE AIR INTO SAID CONNECTION MEANS NEARER SAID FIRE BOX AND (IV) MEANS DISTRIBUTING FLUID FUEL SUBSTANTIALLY UNIFORMLY ALONG AN UPPER EDGE OF SAID PRISMATIC FUEL VOLATILIZER. 